Abstract: A spud bushing system for a mobile offshore arctic drilling structure that permits removal of a spud bushing in a controllable manner even under load. The spud bushing system is characterized by a bushing seat fixed in the structure, an annular bushing surrounding the spud and operative when seated in the bushing seat to support laterally the spud while permitting relative vertical movement therebetween, and plural hydraulic actuators arranged about the periphery of the bushing seat and operable to effect seating and controlled unseating of the bushing.

Abstract: A mobile platform structure, installation and method for use in arctic waters where the dominant environmental loading threats are posed by winter ice pressures and summer ice floes. The structure includes an ice load bearing, submergible substructure and a platform superstructure of approximately equal lateral dimensions. The substructure has a height approximately equal its depth of submergence when ballasted down onto the sea floor and includes a plurality of peripherally arranged, surface accessible spud guides. The spuds are laterally restrained by the spud guides in the top and bottom walls for transmission of lateral loads therebetween at respective vertically spaced apart fulcrum points and are vertically movable in the spud guides for penetration into high shear soils which may be overlaid by relatively low shear soils whereby the shear capacities of both soils combine with the frictional capacity of the structure/sea floor interface to provide high displacement resistance to lateral ice loads.

Abstract: An improved offshore platform base (12) is disclosed having three sets of substantially parallel bulkheads (24, 26, 28) which intersect one another at about 120.degree. forming a repeatable array of contiguous triangular (30) and hexagonal-shaped (34) chambers.

Abstract: A high-energy-absorbing prestressed concrete fender pile, and fendering sem using a plurality of such piles, constructed from high-strength concrete prestressed with longitudinal tensioned strands only partially prestressed such that the longitudinal strands remian elastic to provide high remaining material strength for absorbing high energy impact prior to reaching the yield strength of the strands; the longitudinal tensioned strands are wrapped with an outer spiral wire reinforcement, and the longitudinal strands are preferably stressed to remain elastic until the concrete reches a capacity of 0.003 inch/inch compression strain.